Super spread errors (#1925)
Super spread errors (#1925)

* Add helpful error message for users trying to spread at the front or middle of a list.

* improve wording of spread error message

* Replace error message spread syntax in expression position

chenglou/reason,let-def/reason,let-def/reason,let-def/reason,chenglou/reason,chenglou/reason,facebook/reason,facebook/reason,facebook/reason